I love universe building in Sci-Fi. Especially how different authors take on trying to include some far fetched technology to prove that things are advanced.
In The Unincorporated Man universe there was light that didn't have a source. A room could just be lit with soft light with no obvious source.
In The Mercy of the Gods universe there's centrifuges that work without spinning. You just put stuff in, hit a button, and the separation happens.
Do you have any favourites?